Anaplastic thyroid tumors. Immunohistology

Using an avidin-biotin immunoperoxidase technic, the authors studied 29 anaplastic thyroid tumors (ATTs) to determine the frequency of hormonal (thyroglobulin--TG; calcitonin--CT), epithelial (epithelial membrane antigen, monoclonal keratin), or sarcoma (desmin; alpha-1-antichymotrypsin--ACT; vimentin) markers. Their results indicate that 27% of ATTs stain for TG and none for CT. Fifty-five percent showed epithelial markers, 48% marked for ACT, and 47% for vimentin. Coexpression of keratin and vimentin was found in 39% of cases tested. The expression of the tested antigens did not correlate significantly with histologic pattern (epithelial vs. "sarcomatous"). Of note is the fact that 30% of the ATTs the authors tested expressed none of the markers they examined, indicating total lack of differentiation.